Test device for flat electronic assemblies

ABSTRACT

A test device for testing an electronic board assembly with an exposed surface area with electrical connection locations to be contacted for testing includes a probe ( 32, 45 ) and a drive system for positioning the probe in orthogonal X and Y directions parallel with the surface area. The drive system includes a probe drive ( 11 ) for positioning the probe to contact a selected sub-area of the surface area, the probe drive being movable in all movement coordinates independently of any other probe drives in said test device. The sub-area is selected to include component locations ( 34 ) on the board assembly. Several probe drives ( 11 ) and several probes can be used at one time, each drive having a probe ( 13 ). The probe drives are supported so that the probes ( 13 ) can be moved to contact sub-areas adjacent to each other. The probe is an elongated needle with a contact tip and is mounted for pivotal movement. A probe drive can include two transverse drives ( 15, 17 ) disposed at different distances from the surface area and movable in different directions (X, Y), at least one of the transverse drives including a gimbal mount for holding the needle ( 13 ) for universal movement, the needle being longitudinally movable in the gimbal mount. A vertical drive longitudinally moves the needle and probe toward and away from the surface area.

FIELD OF THE INVENTION

The invention relates to a test device of the type having a probemovable over an electronic board assembly by a controllable drive fortesting the electronic board assembly.

BACKGROUND OF THE INVENTION

Test devices of this kind are used for checking electronic boardassemblies of the most diverse type. Board assemblies of this kind may,for example, be circuit boards, either with or without components, or,for example, highly integrated circuits, of which a plurality aredisposed on a wafer, for IC manufacture. The probes may also be of themost diverse kind, for example electric contact points adapted to beconnected via relay banks to stimulus sources or measuring amplifiers ofa suitable electronic measuring device, or other probes used for othertest methods, such as, for example, inductive or capacitive sensors oroptical scanners, e.g. cameras or microscopes.

For the rapid testing of relatively large board assemblies, such as, forexample, computer motherboards, a plurality of probes are usuallyprovided, which can be positioned independently of one another. Aplurality of probes are frequently also necessary so that when aplurality of electric junction points are to be contacted simultaneouslyit may be possible, for example, to apply a voltage to two junctionpoints and tap off a voltage at a third junction point. Control of theprobes is usually effected by means of sequence programs compiledindividually for a specific board assembly.

Known test devices of this type are always so constructed that all theprobes can be positioned over the total area of the maximum boardassembly which can still be tested on the test device. In theconventional construction, the probes are disposed on slides which areadapted to move over the surface of the board assembly by means ofspindles in the X-direction and the Y-direction. In the case of raisableand lowerable contact points, vertical drives operating in theZ-direction are provided on the slides.

In the known test devices, the slide guides and drives have to bemovable over the entire length of the board assembly for testing, i.e.over considerable lengths which, in the case of a typical PC circuitboard, amount to 30×40 cm for example. With these considerabletraversing distances high spatial resolutions are required. For example,the individual contact pins of modern ICs must be controlled with alength resolution of much less than {fraction (1/10)} mm. Consequently,extremely stable and heavy mountings and drives are required for theslides, resulting in high moving masses.

A disadvantage of such test devices is the low speed of travel from onepoint to another, due to the high moving masses. High masses have to becontinually accelerated and stopped. Decay times also have to be takeninto account.

In modern production lines, for example for electronic equipment, boardassemblies are, however, produced at a speed such that known testdevices of the type according to the preamble are too slow.Consequently, only individual selected board assemblies can be tested,or else a plurality of test devices have to be used in parallel.

In contrast, test devices having a separate probe for each grid point ofthe board assembly, i.e. those operating with stationary probes andwhich do not have the above-mentioned speed problems, have advantages interms of speed. These test devices, however, are disadvantageous interms of circuitry and cost, and particularly in respect of the fixedarrangement of the items under test. They are therefore suitable onlyfor a specific board assembly manufactured on a large scale, while thetest devices with their movable probes, are suitable for rapidchangeover to different board assemblies, i.e. for testing small-scaleproduction runs.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a test device fortesting electronic board assembles with a higher test speed.

With this construction, the advantage of the test devices of the typedescribed above, i.e. to be able to test even larger board assemblieswith just one probe or just a few movable probes, is retained. Comparedwith the known test devices in this area, the advantage lies in the factthat a probe can be driven by a probe drive over just a sub-area of thetotal board assembly area. The traversed distances are thus reduced andthe moving masses can be reduced by several orders of magnitude with thesame or better control accuracy. This results in a traversing speedwhich can be correspondingly increased by several orders of magnitude.For specific applications, e.g. a large board with just one IC, it issufficient to provide the sub-area in the size of the IC. The other fewtest points of the board can be tested in some other way. If a pluralityof probes are provided with corresponding sub-areas, the probe drivescan, for example, be provided to be movable between different sub-areasof the board assembly or be provided in a plurality so as to bestationary covering the total area. With only a slightly increasedmechanical outlay, the test speed is considerably increased as a resultof reducing the driven masses, and this test speed is sufficient evenfor the most up-to-date production lines. This construction also givesthe possibility of considerable further increase of the speed byincreasing the number of probes and probe drives.

Electronic circuit boards which are already equipped with components,the most commonly encountered testing situation, are today predominantlyequipped with ICs of standard size. If the sub-areas are adapted to theICs, it is sufficient to position probe drives over all the ICs or moveone or more probe drives from one IC to the next, in order to be able toapproach all the test points to be covered.

Advantageously, for example, a plurality of probe drives can be disposedin one line and be moved by a main drive successively transversely tothe direction of the line over a larger board. Probe drives can also bearranged to be stationary so as to cover the entire area of a boardassembly for testing, and this may be of advantage particularly forsmaller assemblies for testing. In the case of the latter construction,the test speeds which can be achieved are very high and hithertounthinkable.

Probe drives can be provided on the slides of known test devices insteadof the probes which were hitherto arranged to be stationary there, andbe moved in relatively large steps by the main drives. Even if the maindrives are very slow, as is usual in the prior art, this does notappreciably slow down the total testing time, since, with an optimisedtest sequence program, care can be taken to ensure that the main drivemakes only a few steps while the far larger number of test steps is madeby the very fast probe drives.

If the probe is disposed on a pivotable needle, it can also be movedbeyond the base area of the probe drive. Probe drives can thus bedisposed adjacent one another, with the probes able to operate so as tooverlap in the boundary zone of two probe drives. In the present stateof the art, pivoting drives can be constructed very easily and rapidlyfor the required control electronics. They offer the additionaladvantage of enabling difficultly accessible locations to be reachedwith an inclined needle, for example locations of the kind which areaccessible only from the side but not directly from above.

The provision of two transverse drives as the probe drive isadvantageously provided. With this construction, the pivoting of theneedle can be achieved very easily with two linear drives. Test rigshave proved very rugged and extremely rapid.

Probes can, for example, operate optically, capacitively or withoutcontact in some other manner, the distance from the surface location fortesting on the board assembly being uncritical. In that case a verticaldrive would not be required for the probe. However, at least in the caseof electrically contacting probes constructed as a contact point avertical drive is necessary to set down and raise the contact point ateach test location. In such test devices, the providing a vertical drivefor moving the probe perpendicular to the assembly surface isadvantageous. By moving the contact point relatively to the probe drivethe masses are again very low and the speeds of movement high for thisdrive as well.

It is advantageous to mount the needle for longitudinal displacement inboth gimbal mounts and act on the rear end with the vertical drive tomove the entire needle longitudinally. As a result, the needle is veryeasily constructed to be movable as a whole.

Alternatively, the contact point can be moved relatively to the needle.The needle thus becomes mechanically more complex but the moving massesare further reduced.

It is advantageous to provide a plurality of probe drives havingdifferent spatial resolutions. This creates a large number of possiblevariations for speed optimization. If, for example, an equipped printedcircuit board assembly comprises some highly integrated ICs with a veryclose pattern of connecting pins to be contacted, but, for example,otherwise has a number of discrete components with a coarser pattern,maximum-resolution probe drives operating over a small area can beprovided to approach the ICs and probe drives of lesser resolution canbe used to approach the other contact locations. It is even possible,for example, to use probes movable by slow main drives for these othercontact locations.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example and diagrammatically inthe drawings wherein:

FIG. 1 is a section on the line 1—1 in FIG. 2 through a test devise.

FIG. 2 is a plan view of FIG. 1.

FIG. 3 is a vertical section through one of the probe drives provided inthe test device of FIGS. 1 and 2.

FIG. 4 is a plan view of the probe drive of FIG. 3.

FIG. 5 is a plan view of a test device of a different form ofconstruction with six stationary probe drives.

FIG. 6 is a side elevation of FIG. 5.

FIG. 7 is an elevation of the bottom end of the needle shown in FIG. 3,with a different vertical drive, and

FIG. 8 is an elevation of the top end of the needle shown in FIG. 3,with another variant of the vertical drive.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a test device with two moving probes, this devicebeing of substantially known construction. A frame comprising abaseplate 1 and two cheeks 2 accommodates on the baseplate 1 by means ofdiagrammatically indicated holders 3 a circuit board 4 for testing. Aswill be seen from the Figures, the circuit board 4 is occupied by anarray of ICs or other components.

Two spindles 5, 5′ extend between the cheeks 2 in a traversing directionhereinafter referred to as the X-direction. Cross-members 6, 6′ run onsaid spindles, one being driven by the spindle 5 and the other by thespindle 5′. Slides 7, 7′ run on the cross-members 6, 6′ and are drivenin the Y-direction by transverse spindles 8, 8′ mounted on thecross-members 6, 6′ parallel thereto. Drive motors 9, 9′ are providedfor the spindles 5, 5′ and drive motors 10, 10′ for the transversespindles 8, 8′.

With this conventional test device, the slides 7, 7′ can be traversedover any desired point of the circuit board 4 by appropriate control ofthe motors 9, 9′, 10, 10′. Each of the slides 7, 7′ carries a probedrive 11 for a probe disposed at the end of a needle 13. A verticaldrive is provided in the probe drives 11 to enable the needles 13 to beraised and lowered.

In order to simplify the drawing, leads extending from the probes to anelectronic test device (not shown) and the electronic test device itselfare omitted from the drawing.

By means of the test device of known construction as shown in FIGS. 1and 2, the circuit board 4 can be contacted, for example, at twoelectrical junctions at any time and, for example, the current-flowresistance can be determined.

Conventionally, the test device illustrated is equipped with moreprobes. For example, there may be more than two cross-members provided,and a plurality of slides on each of these, so that a large number ofprobes can be used.

Known test devices of the type shown in FIGS. 1 and 2 hold the probes ina fixed position above the surface by means of the probe drives 11,which are constructed as rigid holders in the X-direction and theY-direction. The drives provided in the X-direction and the Y-directionhave to be moved for each change of location of one of the probe points.The test device illustrated is very large and very heavy in the case ofthe traversing distances required, for example 60 cm in the X-directionand 40 cm in the Y-direction, and with the positioning accuracies ofless than {fraction (1/10)} mm required. High acceleration forces occur.The traversing speeds are correspondingly low.

The probe drives 11 are provided in order significantly to reduce thetest speed, i.e. the average traversing speed of a probe, between twoplaces to be contacted on the circuit board 4. This is explained indetail with reference to FIGS. 3 and 4.

The probe drive 11 is formed in a shaft 12 in the housing, in theinterior of which drives are provided for the needle 13, which bears acontact point 32 as the probe at its bottom end.

First of all, a drive is provided for movement in the X-direction andthe Y-direction, i.e. in the plane of the circuit board 4. It comprisesa slide 15 movable in the X-direction in two rails 14, and a slide 17movable in the Y-direction in rails 16. The linear drives provided inthe X-direction and Y-direction in this way are disposed one above theother with vertical spacing. The slides are driven respectively bymotors 18 and 19, which drive the slides 15, 17 via revolving endlessbelts 20, 21 and drivers 22, 23.

Each of the slides 15 and 17 bears a gimbal mount in the form of a ball24 and 25 mounted for universal rotation in a spherical recess in theslide. The needle 13 extends through a bore in the balls 24 and 25respectively so as to be longitudinally displaceable.

The needle 13 can be brought into any desired pivoted position bymovement of the slides 15 and 17 by means of the motors 18 and 19 in theX-direction and Y-direction. The needle is longitudinally displaceablein the gimbal mounts of the balls 24, 25. A vertical drive providesvertical movement.

In the exemplified embodiment illustrated, the vertical drive comprisesa motor 26 mounted on the housing shaft 12, said motor pivoting an arm28 in the direction of the arrow (FIG. 3) via its output shaft 27. Apivoting arm 30 is mounted on the arm 28 by means of a pivoting bearing29, the top end of the needle 13 being guided on the pivoting arm 30 bymeans of a plain bearing 31 shown in the form of a ring.

When pivoted by the slides 15 and 17 in the X-direction and Y-direction,the needle 13 is pivoted around the balls 24 and 25 respectively of theother slide, so that the top end of the needle 13 deflectscorrespondingly by means of the plain bearing 31. As a result of thedisplaceability of the plain bearing on the pivoting arm 30 and itspivotability about the pivoting bearing 20, the vertical drive can allowthe entire pivoting range of the top end of the needle in permanentengagement.

If the contact point 32 at the bottom end of the needle 13 is requiredto occupy specific vertical positions, the vertical drive illustratedmust take into account the pivoted position of the needle. This can beeffected via appropriate computer control of the motor 26 provided forthe vertical drive, taking into account the respective position of theslides 15 and 17 pivoting in the X-direction and the Y-direction.

As shown in FIG. 3 in the bottom part of the drawing, the needle 13 can,by its contact point 32, successively approach connecting tags 33 of anIC 34 soldered on the circuit board 4.

With the test device shown in its entirety in FIGS. 1 to 4, the circuitboard 4 illustrated is tested with a test program which optimizes thedistances traversed. The main drives comprising the motors 9, 9′, 10,10′ are used as little as possible. They respectively move the probedrives 11 into a new position in which these drives can very rapidlyreach a very large number of points by the much faster movement of thelightweight needle 13, the points being, for example, the variousconnecting tags 33 of the IC 34 shown in FIG. 3.

FIGS. 5 and 6 show a basic constructional variant in which a pluralityof the probe drives 11 shown in FIGS. 3 and 4, namely, in theexemplified embodiment, six drives, are secured to one another in afixed arrangement and are disposed by means of holders (not shown) abovea circuit board 35 for testing. The six probe drives 11 shown, for theprobes constructed as needles 13, are in this case stationary above thecircuit board 35 during the test operation. Only the needles 13 move bymeans of the drives explained with reference to FIGS. 3 and 4, so thatall the points to be contacted on the circuit board 35 can be reached. Asolution of this kind is particularly suitable for smaller circuitboards.

In a variant, for example, a line consisting of a plurality of adjacentprobe drives 11, as will be seen from the side in FIG. 6, are disposedin the form of a line on one of the cross-members 6, 6′ of the testdevice shown in FIGS. 1 and 2. This line of probe drives can be movedover the circuit board 4 by moving the respective cross-member havingthe drive 5, 9; 5′, 9′ acting in the X-direction.

A number of other variants are possible compared with the embodimentsillustrated. The probe drive 11 explained in FIGS. 3 and 4 comprises avertical drive which moves the needle 13 vertically as a whole.Alternatively, as shown in FIG. 7, a needle 43 can carry a verticaldrive 44 which moves the contact point 45 in the direction of the arrowrelatively to the needle 43. The vertical drive can thus besignificantly accelerated by reducing the vertically moving masses. Theconstruction shown in FIGS. 3 and 4 is also simplified, since thevertical drive shown there is dispensed with. The needle 13 then nolonger has to be mounted for longitudinal displacement in the two gimbalmounts, i.e. in the two balls 24 and 25. It can be held to belongitudinally stationary in one of the balls.

FIG. 8 shows another variant for the vertical drive. As shown in FIGS. 3and 4, the needle 13 is guided for longitudinal displacement in theballs 24 and 25. It is driven vertically from its top end, but with adifferent type of drive from that shown in FIGS. 3 and 4.

As shown in FIG. 8, a probe 47 is supported relative to the slide 17 atthe top end of the needle 13 by means of a coil spring 48 and pressesthe needle 13 upwards. A plate 50 which is vertically movable inparallel relationship by means of a drive member 49 acts from above onthe probe 47 and provides vertical movement of needle 13 against theforce of the spring 48.

At the same time the plate 50 may have on its underside a recess 51 inthe form of an ellipsoid cup, which is formed in two radii adapted tothe spacing around the balls 24 and 25. The computing work forcontrolling the vertical drive motor 26 can thus be reduced.

In the preferred embodiment illustrated, the probe drive is in each caseconstructed as a needle pivoting drive. As shown by FIG. 6, for example,this has the advantage that the probe at the bottom end of the needle 13can be moved beyond the base area of the respective probe drive 11, i.e.to overlap between adjacent probe drives. A comparison with FIG. 2 willshow that the two probe drives 11 can be traversed side by sidelaterally and operate in overlapping relationship in the boundary zone.

Drives other than those illustrated can be used as the needle pivotingdrives. For example, the needle can be pivoted about a central pivotingpoint by means of suitable drives. It can also be mounted above theslides 15 and 17 shown in FIGS. 3 and 4 to be pivotable at a fixedpoint, for example at the location of the bearing ring 31, i.e. at itstop end. The slides 15 and 17 can then engage the needle by slotsextending parallel to their rails.

It should also be noted that in this description, which is limited tothe mechanical control, the electrical connections to the contact point32 have been omitted. This is connected electrically through the needle13 to a connecting lead 52 extending to an electronic tester (notshown). Depending on the test situation, in this tester the contactpoint 32 can be connected to a measuring amplifier or a stimulus source,e.g. a constant-voltage source or a constant-current source. Referenceshould be made to the appropriate extensive literature in connectionwith the appropriate test methods. For example, guard tests or parasitictransistor tests can be carried out in accordance with DE 41 10 551 C1.

Instead of the contact point 32 illustrated, which serves for electricalcontacting, the needle 13 shown in the embodiments can also carry otherprobes, for example inductive or capacitive sensors, which in theexample of FIG. 3 are not contacted with the tags 33, but brought into aspecific spacing therefrom. The probes may also, for example, be opticaldevices, such as cameras or microscopes with a connected video camera,for high-resolution observation. Devices of this kind can also be usedparticularly in miniaturised form for testing integrated circuits onwafers.

Instead of the preferred needle pivoting drive for the probe as shown inthe drawings, other mechanical drives can also be used as probe drives.For example, simple XY-drives, in which the X-drive is mounted on theY-drive, can be used, with which a test point, for example in the formof a needle, can be moved in parallel relationship. Drives which pivotin a plane in superimposed relationship parallel to the circuit boardfor testing can also be used.

The test device explained with reference to FIGS. 1 to 4 can also becompleted by an additional coarse vertical drive, by means of which theprobe drives 11 are held on the slides 7, 7′. The drives may be slowvertical drives which are used only for special cases, for example whenunusual vertical movements are required during the traversing of alarger component, where such vertical movements cannot be provided bythe vertical drives in the probe drive 11.

What is claimed is:
 1. A test device for testing an electronic boardassembly having an exposed surface area comprising a plurality ofsub-areas with electrical connection locations to be contacted fortesting, the device comprising a probe (32, 45) for contacting locationson said exposed surface area for testing; a probe drive (11) for X-Ypositioning said probe in any of a plurality of said locations to becontacted within any two-dimensional sub-area within said exposedsurface area, said sub-area being smaller than said exposed surfacearea, and drive means for successively positioning said probe drive tomore than one sub-area whereby said probe can contact and test locationsin plural sub-areas of said exposed surface area.
 2. The test device ofclaim 1 wherein each said sub-area is selected to include componentlocations (34) on said board assembly.
 3. The test device of claim 1comprising a plurality of probe drives (11), each said drive having aprobe (13), and means for supporting and independently operating saidprobe drives so that ends of said probes (13) can be moved to contactlocations in sub-areas adjacent to each other.
 4. The test device ofclaim 1 wherein said drive means comprises a main drive having driveelements (7, 7′) connected to position said probe drive (11) relative tosaid surface area.
 5. The test device according to claim 1 wherein saidprobe (32) comprises an elongated needle (13) having a probe end, saidneedle being mounted for pivotal movement and being driven to selectedangular positions relative to said surface area by said probe drive. 6.The test device according to claim 5 including a vertical drive forlongitudinally moving said needle (13) to move said probe end (32, 45)toward and away from said surface area.
 7. The test device according toclaim 6 wherein said probe drive comprises X and Y transverse drives(15, 17) at different distances from said surface area, each of saidtransverse drives comprising a gimbal mount for holding said needle,said needle being longitudinally movable in said gimbal mounts and beingactuated by a vertical drive (26, 30) at an end of said needle remotefrom said probe end.
 8. The test device according to claim 5 whereinsaid probe end comprises an extendible portion and said vertical drivemoves said probe end relative to said needle.
 9. The test deviceaccording to claim 1 including a plurality of probe drives havingdifferent spatial resolutions.
 10. A test device for testing anelectronic board assembly having an exposed surface area with electricalconnection locations to be contacted for testing, the device comprisinga plurality of probes (32, 45) for contacting locations on said surfacearea for testing; a plurality of probe drives (11) each for positioningone said probe to said locations to be contacted within atwo-dimensional subarea within said exposed surface area, each saidsub-area being smaller than said surface area, each said probe beingindependently movable by its probe drive; and means for mounting eachsaid probe drive in a substantially fixed location over said onesub-area of said surface area.
 11. A test device according to claim 10wherein said sub-areas are adjacent to each other.
 12. The test deviceaccording to claim 11 wherein said adjacent sub-areas overlap.
 13. Thetest device of claim 11 wherein each said sub-area is selected toinclude component locations (34) on said board assembly.
 14. The testdevice of claim 10 wherein each said probe drive comprises a probe (13),and means for supporting and independently operating said probe drivesso that ends of said probes (13) can be moved to contact locations insaid sub-areas adjacent to each other.
 15. The test device according toclaim 10 wherein said probe (32) comprises an elongated needle (13)having a probe end, said needle being mounted for pivotal movement andbeing driven to selected angular positions relative to said surface areaby said probe drive.
 16. The test device according to claim 15 includinga vertical drive for longitudinally moving said needle (13) to move saidprobe end (32, 45) toward and away from said surface area.
 17. The testdevice according to claim 15 wherein each said probe drive comprises Xand Y transverse drives (15, 17) at different distances from saidsurface area, each of said transverse drives comprising a gimbal mountfor holding said needle, said needle being longitudinally movable inboth said gimbal mounts and being actuated by a vertical drive (26, 30)at an end of said needle remote from said probe end.
 18. The test deviceaccording to claim 15 wherein said probe end comprises an extendibleportion and said vertical drive moves said probe end relative to saidneedle.
 19. The test device according to claim 10 including a pluralityof probe drives having different spatial resolutions.
 20. A test devicefor testing an electronic board assembly having an exposed surface areawith electrical connection locations to be contacted for testing, thedevice comprising at least one probe drive (11); and at least one probe(32, 45) comprising an elongated needle (13) having a probe end, saidneedle being mounted on one said probe drive for pivotal movement andbeing driven to selected angular positions relative to said surface areaby said at least one probe drive for contact within a two-dimensionalsub-area within said surface area, said sub-area being smaller than saidsurface area; each said probe drive comprises X and Y transverse drives(15, 17) at different distances from said surface area, each of saidtransverse drives comprising a gimbal mount for holding said needle,said needle being longitudinally movable in both said gimbal mounts andbeing actuated by a vertical drive (26, 30) at an end of said needleremote from said probe end.